In connection with a cooling structure of a conventional secondary battery, by way of example, Japanese Patent Laying-Open No. 2005-71784 discloses a structure of a stacked type battery having a plurality of unit batteries stacked in series, in which a cooling tab is attached to a plurality of collectors. Each of the unit batteries is formed by connecting in series a collector having a positive electrode active material on one surface and a negative electrode active material on the rear surface, to another collector, with a polymer electrolyte posed therebetween. In the stacked type battery, surface area, thickness or the like of the cooling tabs is adjusted such that heat radiating effect of the cooling tab at the center of thickness in stacking becomes the highest and the heat radiating effect of cooling tab decreases toward opposite ends in the thickness direction.
In the stacked type battery described above, the cooling tab protrudes from the collector. Specifically, in the stacked type battery described above, widthwise length of the battery unavoidably increases as the cooling tab is provided. Japanese Patent Laying-Open No. 2005-71784 does not specifically disclose any specific solution to such a problem.